1. Field
One or more embodiments of the present invention relates to an image correction apparatus, method and medium, and more particularly, to an image correction apparatus, method and medium which can perform color component correction and geometric correction using the property of a projector projecting light of a plurality of color components of an input image at different times.
2. Description of the Related Art
Conventional projectors include liquid crystal display (LCD), digital light processing (DLP), cathode ray tube (CRT), and liquid crystal on silicon (LCoS) projectors.
Specifically, CRT projectors are direct-view type projectors, and LCD, DLP and LCoS projectors are projection type projectors. A CRT, which is usually employed in a direct-view type projector, includes a fluorescent panel on which red (R), green (G) and blue (B) phosphor dots and black stripes are formed. The CRT also includes R, G and B electron guns which emit electron beams corresponding to an input image. When the electron beams reach particular R, G and B phosphor dots via a shadow mask, the R, G and B phosphor dots are illuminated and produce colors.
LCD projectors, which are the most widely used projectors, produce an image by splitting light into R, G, and B components using pixels of three liquid crystal panels and collecting the split R, G and B components using a lens.
DLP projectors integrate thousands of microscopically small mirrors corresponding to pixels on a chip called a ‘digital mirror device (DMD).” The mirrors tilt to reflect light at varying angles and, in so doing, produce an image from an input signal.
LCoS projectors are a relatively new technology which combines the LCD and DLP technologies. In LCoS projectors, LCDs are integrated on a silicon wafer, and circuits are formed on the LCDs. LCoS projectors consume low power, and provide high-resolution, full-color images. In addition, there is less of a limitation on the number of pixels in LCoS projectors than in LCD or DLP projectors. Therefore, high-resolution panels can be manufactured at low cost, one of the reasons why LCoS projectors are widely used.
Of the four types of projectors described above, DLP projectors split light from a light source into R, G and B components using a color wheel and project the R, G and B components at different times.
In order to perform image correction such as color component correction and geometric correction, a DLP projector temporarily stops projecting a current image and instead projects an image for color component correction and geometric correction.
For example, in the case of color component correction, a DLP projector sequentially projects (R, 0, 0), (0, G, 0) and (0, 0, B) images onto an entire projection plane in order to obtain a color mixing matrix and surface reflectivity. Then, the DLP projector performs color component correction on an input image so that a projected image can more closely resemble a target image.
In the case of geometric correction, the DLP projector estimates a geometric model of a projection plane by scanning, for example, a grating pattern of the projection plane and performs geometric correction based on the estimated geometric model.
In the case of color component correction, when an object is changed, the DLP projector has to update an image of the object by repeatedly projecting an image, in order to continuously obtain the color mixing matrix and the surface reflectivity. In the case of geometric correction, the scanning of a pattern may cause eye strain. Furthermore, since an image being projected is temporarily stopped to perform color component correction and geometric correction, user convenience may be undermined.
Korean Patent Publication No. 2004-099166 discloses a projection system generating a calibration signal for a white image and calibration signals for primary subtractive colors, projecting the calibration signals onto a screen, picking up a projected image using an image sensor, and generating image correction information using difference values between the picked-up signals. The conventional art is designed to generate image correction information using difference values between calibration images. However, the conventional art does not suggest solutions to problems which may occur when a DLP projector performs color component correction and geometric correction.